Lithographic apparatus

ABSTRACT

A lithographic apparatus includes a patterning device support to support a patterning device, the patterning device system including a moveable structure movably arranged relative to an object, a patterning device holder movably arranged relative to the movable structure to hold the patterning device, an actuator to move the movable structure relative to the object, and an ultra short stroke actuator to move the patterning device holder with respect to the movable structure; a substrate support to hold a substrate; a projection system to project a patterned radiation beam onto a target portion of the substrate; a transmission image sensor for measuring a position of the patterned radiation beam downstream of the projection system; and a calibrator for determining a relationship between magnitude of an applied control signal to the ultra short stroke actuator and resulting change in position of the patterned radiation beam and/or patterning device holder and/or patterning device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application61/639,545, which was filed on 27 Apr. 2012, and which is incorporatedherein in its entirety by reference.

FIELD

The present invention relates to a lithographic apparatus and a devicemanufacturing method.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In that instance, a patterning device, whichis alternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.comprising part of, one, or several dies) on a substrate (e.g. a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. However, another fluid may besuitable, particularly a wetting fluid, an incompressible fluid and/or afluid with higher refractive index than air, desirably a higherrefractive index than water. Fluids excluding gases are particularlydesirable. The point of this is to enable imaging of smaller featuressince the exposure radiation will have a shorter wavelength in theliquid. (The effect of the liquid may also be regarded as increasing theeffective numerical aperture (NA) of the system and also increasing thedepth of focus.) Other immersion liquids have been proposed, includingwater with solid particles (e.g. quartz) suspended therein, or a liquidwith a nano-particle suspension (e.g. particles with a maximum dimensionof up to 10 nm). The suspended particles may or may not have a similaror the same refractive index as the liquid in which they are suspended.Other liquids which may be suitable include a hydrocarbon, such as anaromatic, a fluorohydrocarbon, and/or an aqueous solution.

In the lithographic apparatus, use is made of a movable support to holdand position an exchangeable object such as the substrate or thepatterning device. In a scanning type lithographic apparatus, a movablesupport is used to support the substrate in order to make the scanningmovement. The patterning device may also be supported on a movablesupport. The movable support is able to position the substrate orpatterning device with high accuracy.

To obtain a high accuracy, a known movable support is assembled from along stroke part, movable with respect to a reference object such as aframe, and a short stroke part, movably arranged with respect to thelong stroke part. The short stroke part is configured to support theexchangeable object. The maximum stroke of the long stroke part withrespect to reference object is relatively large, while the stroke of theshort stroke part with respect to the long stroke part is relativelysmall.

A long stroke actuator is provided to actuate the long stroke part withrespect to the reference object. A short stroke actuator is provided toactuate the short stroke part with respect to the long stroke part. Suchlong stroke actuator is for instance a linear motor, and may not be veryaccurate. The main task of the long stroke actuator is to keep thestator part of the short-stroke actuator in the vicinity of the movingpart. The short stroke actuator is designed to position the short strokepart with high accuracy.

In order to control the position of the exchangeable object, theposition of the second support system for supporting the substrate isdetermined by a position measurement system, for instance aninterferometer system or an encoder system. This measurement is forinstance performed in three planar degrees of freedom or in six degreesof freedom. The measured position is compared with a desired position.The position error, i.e. the difference between measured and desiredposition is fed into a controller which on the basis of this signalprovides a control signal which is used to actuate the short strokeactuator.

The long stroke actuator is controlled by using a signal based on thedifference between the actual position of the short stroke part and thelong stroke part as an input signal for the long stroke actuatorcontroller. The output of this controller makes the long stroke partfollow the movements of the short stroke part, therewith keeping thedesired position of the short stroke part within the range of the shortstroke actuator.

The short stroke actuator may be of the Lorentz type to enable isolationfrom long-stroke vibrations. Such Lorentz type actuator has a smallstiffness. Any other type of actuator having a small stiffness and highaccuracy may also be used accurately to control the position of theexchangeable object support by the movable support. The input of aLorentz actuator is an electrical current, substantially proportional tothe desired force.

The force-type-actuator in the stages may limit the achievablefeed-forward effect from one stage to the other (e.g. substrate tableerror fed to patterning device support). In this feed-forward, theposition error of one stage needs to be differentiated twice to generatea feed-forward force, which costs one sample delay. This leads to adelayed response of the other stage, limiting positioning accuracy ofthe stages relative to each other. This feed-forward performance isfurther limited by calculation delay, amplifier (DAC) delay, andhigher-order dynamics of the short-stroke system.

SUMMARY

It is desirable to increase the accuracy of positioning of anexchangeable object such as a patterning device, supported by a movablesupport.

According to an aspect of the invention, there is provided alithographic apparatus comprising: a patterning device supportconstructed to support a patterning device, the patterning device beingcapable of imparting a radiation beam with a pattern in itscross-section to form a patterned radiation beam, the patterning devicesupport comprising a moveable structure movably arranged with respect toan object, a patterning device holder movably arranged with respect tothe movable structure and configured to hold the patterning device, anactuator configured to move the movable structure with respect to theobject, and an ultra short stroke actuator configured to move thepatterning device holder with respect to the movable structure; asubstrate support constructed to hold a substrate; and a projectionsystem configured to project the patterned radiation beam onto a targetportion of the substrate, a position measurement system for measuring asubstrate positional error which is a difference between a desiredposition of the substrate relative to a reference object and an actualposition of the substrate relative to the reference object; and acontroller configured to move the actuator and the ultra short strokeactuator at least partly on the basis of the substrate positional error.

According to an aspect of the invention, there is provided alithographic apparatus comprising: a patterning device supportconstructed to support a patterning device, the patterning device beingcapable of imparting a radiation beam with a pattern in itscross-section to form a patterned radiation beam, the patterning devicesupport comprising a moveable structure movably arranged with respect toan object, a patterning device holder movably arranged with respect tothe movable structure and configured to hold the patterning device, anactuator configured to move the movable structure with respect to theobject, and an ultra short stroke actuator configured to move thepatterning device holder with respect to the movable structure; asubstrate support constructed to hold a substrate; and a projectionsystem configured to project the patterned radiation beam onto a targetportion of the substrate; a position measurement system for measuring asubstrate positional error which is a difference between a desiredposition of the substrate relative to a reference object and an actualposition of the substrate relative to the reference object; and acontroller configured to move the ultra short stroke actuatorexclusively on the basis of: the substrate positional error andoptionally a measured position of the patterning device holder relativeto the moveable structure.

According to an aspect of the invention, there is provided alithographic apparatus comprising: a patterning device supportconstructed to support a patterning device, the patterning device beingcapable of imparting a radiation beam with a pattern in itscross-section to form a patterned radiation beam, the patterning devicesystem comprising a moveable structure movably arranged with respect toan object, a patterning device holder movably arranged with respect tothe movable structure and configured to hold the patterning device, anactuator configured to move the movable structure with respect to theobject, and an ultra short stroke actuator configured to move thepatterning device holder with respect to the movable structure; asubstrate support constructed to hold a substrate; and a projectionsystem configured to project the patterned radiation beam onto a targetportion of the substrate, a position measurement system for measuring aposition of the patterning device holder and/or patterning devicerelative to the movable structure; and a controller configured to movethe ultra short stroke actuator on the basis of a positional errorsignal and the position of the patterning device holder and/orpatterning device measured by the position measurement system.

According to an aspect of the invention, there is provided alithographic apparatus comprising: a patterning device supportconstructed to support a patterning device, the patterning device beingcapable of imparting a radiation beam with a pattern in itscross-section to form a patterned radiation beam, the patterning devicesystem comprising a moveable structure movably arranged with respect toan object, an patterning device holder movably arranged with respect tothe movable structure and configured to hold the patterning device, anactuator configured to move the movable structure with respect to theobject, and an ultra short stroke actuator configured to move thepatterning device holder with respect to the movable structure; asubstrate support constructed to hold a substrate; a projection systemconfigured to project the patterned radiation beam onto a target portionof the substrate; and an open loop controller configured to move theultra short stroke actuator on the basis of a positional error signal.

According to an aspect of the invention, there is provided alithographic apparatus comprising: a patterning device supportconstructed to support a patterning device, the patterning device beingcapable of imparting a radiation beam with a pattern in itscross-section to form a patterned radiation beam, the patterning devicesystem comprising a moveable structure movably arranged with respect toan object, a patterning device holder movably arranged with respect tothe movable structure and configured to hold the patterning device, anactuator configured to move the movable structure with respect to theobject, and an ultra short stroke actuator configured to move thepatterning device holder with respect to the movable structure; asubstrate support constructed to hold a substrate; a projection systemconfigured to project the patterned radiation beam onto a target portionof the substrate, a transmission image sensor for measuring a positionof the patterned radiation beam downstream of the projection system; anda calibrator for determining a relationship between magnitude of anapplied control signal to the ultra short stroke actuator and resultingchange in position of the patterned radiation beam and/or patterningdevice holder and/or patterning device.

According to an aspect of the invention, there is provided alithographic apparatus comprising: a patterning device supportconstructed to support a patterning device, the patterning device beingcapable of imparting a radiation beam with a pattern in itscross-section to form a patterned radiation beam; a substrate supportconstructed to hold a substrate; and a projection system configured toproject the patterned radiation beam onto a target portion of thesubstrate, wherein the patterning device supports comprises: a moveablestructure movably arranged with respect to an object, a patterningdevice holder movably arranged with respect to the movable structure andconfigured to hold the patterning device; an actuator configured to movethe movable structure with respect to the object; and an ultra shortstroke actuator configured to move the patterning device holder withrespect to the movable structure and comprising a plurality of actuatorspositioned around at least part of a circumference of the patterningdevice holder.

According to an aspect of the invention, there is provided alithographic apparatus comprising: a patterning device supportconstructed to support a patterning device, the patterning device beingcapable of imparting a radiation beam with a pattern in itscross-section to form a patterned radiation beam, the patterning devicesupport comprising a moveable structure movably arranged with respect toan object, an patterning device holder movably arranged with respect tothe movable structure and configured to hold the patterning device, anactuator configured to move the movable structure with respect to theobject, and an ultra short stroke actuator configured to move thepatterning device holder with respect to the movable structure; asubstrate support constructed to hold a substrate; and a projectionsystem configured to project the patterned radiation beam onto a targetportion of the substrate, wherein the ultra short stroke actuator isglued between the patterning device holder and moveable structure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIG. 2 depicts, in cross-section, a barrier member which may be used inan embodiment of the present invention as an immersion liquid supplysystem;

FIG. 3 depicts schematically a cross-sectional view of selected parts ofa lithographic apparatus according to an embodiment of the invention;

FIG. 4 depicts, in cross-section, an ultra short stroke actuatoraccording to an embodiment of the invention;

FIG. 5 illustrates a control scheme for a patterning device supportaccording to an embodiment of the invention;

FIG. 6 illustrates a control scheme for a patterning device supportaccording to an embodiment of the invention;

FIG. 7 illustrates a method of calibrating an ultra short strokeactuator controller according to an embodiment of the invention;

FIG. 8 illustrates, in plan, a plurality of ultra short stroke actuatorsaccording to an embodiment of the invention; and

FIG. 9 illustrates, in cross-section, use of the plurality of ultrashort stroke actuators of FIG. 8 during patterning device bendingaccording to an embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus comprises:

-   -   an illumination system (illuminator) IL configured to condition        a radiation beam B (e.g. UV radiation, DUV radiation or EUV        radiation);    -   a support structure (e.g. a mask table) MT constructed to        support a patterning device (e.g. a mask) MA and connected to a        first positioner PM configured to accurately position the        patterning device in accordance with certain parameters;    -   a substrate table (e.g. a wafer table) WT constructed to hold a        substrate (e.g. a resist-coated wafer) W and connected to a        second positioner PW configured to accurately position the        substrate in accordance with certain parameters; and    -   a projection system (e.g. a refractive projection lens system)        PS configured to project a pattern imparted to the radiation        beam B by patterning device MA onto a target portion C (e.g.        comprising one or more dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation.

The support structure MT holds the patterning device. The supportstructure MT holds the patterning device in a manner that depends on theorientation of the patterning device, the design of the lithographicapparatus, and other conditions, such as for example whether or not thepatterning device is held in a vacuum environment. The support structureMT can use mechanical, vacuum, electrostatic or other clampingtechniques to hold the patterning device. The support structure MT maybe a frame or a table, for example, which may be fixed or movable asrequired. The support structure MT may ensure that the patterning deviceis at a desired position, for example with respect to the projectionsystem. Any use of the terms “reticle” or “mask” herein may beconsidered synonymous with the more general term “patterning device.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a reflective mask). The lithographicapparatus may be of a type having two (dual stage) or more substratetables (and/or two or more patterning device tables). In such “multiplestage” machines the additional tables may be used in parallel, orpreparatory steps may be carried out on one or more tables while one ormore other tables are being used for exposure. In an embodiment, thelithographic apparatus is a multi-stage apparatus comprising two or moretables located at the exposure side of the projection system, each tablecomprising and/or holding one or more objects. In an embodiment, one ormore of the tables may hold a radiation-sensitive substrate. In anembodiment, one or more of the tables may hold a sensor to measureradiation from the projection system. In an embodiment, the multi-stageapparatus comprises a first table configured to hold aradiation-sensitive substrate (i.e., a substrate table) and a secondtable not configured to hold a radiation-sensitive substrate (referredto hereinafter generally, and without limitation, as a measurementand/or cleaning table). The second table may comprise and/or may holdone or more objects, other than a radiation-sensitive substrate. Suchone or more objects may include one or more selected from the following:a sensor to measure radiation from the projection system, one or morealignment marks, and/or a cleaning device (to clean, e.g., the liquidconfinement structure).

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source and the lithographic apparatus may beseparate entities, for example when the source is an excimer laser. Insuch cases, the source is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source may be an integral part of thelithographic apparatus, for example when the source is a mercury lamp.The source SO and the illuminator IL, together with the beam deliverysystem BD if required, may be referred to as a radiation system.

The illuminator IL may comprise an adjuster AM configured to adjust theangular intensity distribution of the radiation beam. Generally, atleast the outer and/or inner radial extent (commonly referred to asσ-outer and σ-inner, respectively) of the intensity distribution in apupil plane of the illuminator can be adjusted. In addition, theilluminator IL may comprise various other components, such as anintegrator IN and a condenser CO. The illuminator may be used tocondition the radiation beam, to have a desired uniformity and intensitydistribution in its cross-section. Similar to the source SO, theilluminator IL may or may not be considered to form part of thelithographic apparatus. For example, the illuminator IL may be anintegral part of the lithographic apparatus or may be a separate entityfrom the lithographic apparatus. In the latter case, the lithographicapparatus may be configured to allow the illuminator IL to be mountedthereon. Optionally, the illuminator IL is detachable and may beseparately provided (for example, by the lithographic apparatusmanufacturer or another supplier).

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the support structure (e.g., mask table) MT, and ispatterned by the patterning device. Having traversed the patterningdevice MA, the radiation beam B passes through the projection system PS,which focuses the beam onto a target portion C of the substrate W. Withthe aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam B.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe patterning device MA with respect to the path of the radiation beamB, e.g. after mechanical retrieval from a mask library, or during ascan. In general, movement of the support structure MT may be realizedwith the aid of a long-stroke module (coarse positioning) and ashort-stroke module (fine positioning), which form part of the firstpositioner PM. Similarly, movement of the substrate table WT may berealized using a long-stroke module and a short-stroke module, whichform part of the second positioner PW. In the case of a stepper (asopposed to a scanner) the support structure MT may be connected to ashort-stroke actuator only, or may be fixed. Patterning device MA andsubstrate W may be aligned using patterning device alignment marks M1,M2 and substrate alignment marks P1, P2. Although the substratealignment marks as illustrated occupy dedicated target portions, theymay be located in spaces between target portions (these are known asscribe-lane alignment marks). Similarly, in situations in which morethan one die is provided on the patterning device MA, the patterningdevice alignment marks may be located between the dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the support structure MT and the substrate table WT arekept essentially stationary, while an entire pattern imparted to theradiation beam is projected onto a target portion C at one time (i.e. asingle static exposure). The substrate table WT is then shifted in the Xand/or Y direction so that a different target portion C can be exposed.In step mode, the maximum size of the exposure field limits the size ofthe target portion C imaged in a single static exposure.

2. In scan mode, the support structure MT and the substrate table WT arescanned synchronously while a pattern imparted to the radiation beam isprojected onto a target portion C (i.e. a single dynamic exposure). Thevelocity and direction of the substrate table WT relative to the supportstructure MT may be determined by the (de-)magnification and imagereversal characteristics of the projection system PS. In scan mode, themaximum size of the exposure field limits the width (in the non-scanningdirection) of the target portion in a single dynamic exposure, whereasthe length of the scanning motion determines the height (in the scanningdirection) of the target portion.

3. In another mode, the support structure MT is kept essentiallystationary holding a programmable patterning device, and the substratetable WT is moved or scanned while a pattern imparted to the radiationbeam is projected onto a target portion C. In this mode, generally apulsed radiation source is employed and the programmable patterningdevice is updated as required after each movement of the substrate tableWT or in between successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizesprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

In many lithographic apparatus a fluid, in particular a liquid forexample an immersion liquid, is provided between the final element ofthe projection system and the substrate using a liquid supply system IHto enable imaging of smaller features and/or increase the effective NAof the apparatus. An embodiment of the invention is described furtherbelow with reference to such an immersion apparatus, but may equally beembodied in a non-immersion apparatus. Arrangements to provide liquidbetween a final element of the projection system and the substrate canbe classed into at least two general categories. These are the bath typearrangement and the so called localized immersion system. In the bathtype arrangement substantially the whole of the substrate and optionallypart of the substrate table is submersed in a bath of liquid. The socalled localized immersion system uses a liquid supply system in whichliquid is only provided to a localized area of the substrate. In thelatter category, the space filled by liquid is smaller in plan than thetop surface of the substrate and the area filled with liquid remainssubstantially stationary relative to the projection system while thesubstrate moves underneath that area. Another arrangement, to which anembodiment of the invention is directed, is the all wet solution inwhich the liquid is unconfined. In this arrangement substantially thewhole top surface of the substrate and all or part of the substratetable is covered in immersion liquid. The depth of the liquid coveringat least the substrate is small. The liquid may be a film such as a thinfilm, of liquid on the substrate.

In an embodiment, the liquid is distilled water, although another liquidcan be used. An embodiment of the present invention will be describedwith reference to liquid.

An arrangement which has been proposed is to provide the liquid supplysystem with a liquid confinement member which extends along at least apart of a boundary of the space between the final element of theprojection system and the substrate table. Such an arrangement isillustrated in FIG. 2. The liquid confinement member is substantiallystationary relative to the projection system in the XY plane thoughthere may be some relative movement in the Z direction (in the directionof the optical axis). A seal is formed between the liquid confinementand the surface of the substrate. In an embodiment, a seal is formedbetween the liquid confinement structure and the surface of thesubstrate and may be a contactless seal such as a gas seal. Such asystem is disclosed in United States patent application publication no.US 2004-0207824.

FIG. 2 schematically depicts a localized liquid supply system with afluid handling structure 12. The fluid handling structure extends alongat least a part of a boundary of the space between the final element ofthe projection system and the substrate table WT or substrate W. (Pleasenote that reference in the following text to surface of the substrate Walso refers in addition or in the alternative to a surface of thesubstrate table, unless expressly stated otherwise.) The fluid handlingstructure 12 is substantially stationary relative to the projectionsystem in the XY plane though there may be some relative movement in theZ direction (in the direction of the optical axis). In an embodiment, aseal is formed between the barrier member and the surface of thesubstrate W and may be a contactless seal such as a fluid seal,desirably a gas seal.

The fluid handling structure 12 at least partly contains liquid in thespace 11 between a final element of the projection system PS and thesubstrate W. A contactless seal 16 to the substrate W may be formedaround the image field of the projection system so that liquid isconfined within the space between the substrate W surface and the finalelement of the projection system PS. The space is at least partly formedby the fluid handling structure 12 positioned below and surrounding thefinal element of the projection system PS. Liquid is brought into thespace below the projection system and within the fluid handlingstructure 12 by liquid inlet 13. The liquid may be removed by liquidoutlet 13. The fluid handling structure 12 may extend a little above thefinal element of the projection system. The liquid level rises above thefinal element so that a buffer of liquid is provided. In an embodiment,the fluid handling structure 12 has an inner periphery that at the upperend closely conforms to the shape of the projection system or the finalelement thereof and may, e.g., be round. At the bottom, the innerperiphery closely conforms to the shape of the image field, e.g.,rectangular, though this need not be the case.

In an embodiment, the liquid is contained in the space 11 by a gas seal16 which, during use, is formed between the bottom of the fluid handlingstructure 12 and the surface of the substrate W. The gas seal is formedby gas, e.g. air or synthetic air but, in an embodiment, N₂ or anotherinert gas. The gas in the gas seal is provided under pressure via inlet15 to the gap between fluid handling structure 12 and substrate W. Thegas is extracted via outlet 14. The overpressure on the gas inlet 15,vacuum level on the outlet 14 and geometry of the gap are arranged sothat there is a high-velocity gas flow 16 inwardly that confines theliquid. The force of the gas on the liquid between the fluid handlingstructure 12 and the substrate W contains the liquid in a space 11. Theinlets/outlets may be annular grooves which surround the space 11. Theannular grooves may be continuous or discontinuous. The flow of gas 16is effective to contain the liquid in the space 11. Such a system isdisclosed in United States patent application publication no. US2004-0207824.

In an embodiment, the lithographic apparatus comprises a liquidconfinement structure that has a liquid removal device having an inletcovered with a mesh or similar porous material. The mesh or similarporous material provides a two-dimensional array of holes contacting theimmersion liquid in a space between the final element of the projectionsystem and a movable table (e.g., the substrate table). In anembodiment, the mesh or similar porous material comprises a honeycomb orother polygonal mesh. In an embodiment, the mesh or similar porousmaterial comprises a metal mesh. In an embodiment, the mesh or similarporous material extends all the way around the image field of theprojection system of the lithographic apparatus. In an embodiment, themesh or similar porous material is located on a bottom surface of theliquid confinement structure and has a surface facing towards the table.In an embodiment, the mesh or similar porous material has at least aportion of its bottom surface generally parallel with a top surface ofthe table.

Many other types of liquid supply system are possible. The presentinvention is neither limited to any particular type of liquid supplysystem, nor to immersion lithography. The invention may be appliedequally in any lithography. In an EUV lithographic apparatus, the beampath is substantially evacuated and immersion arrangements describedabove are not used.

A control system or controller 500 controls the overall operations ofthe lithographic apparatus and in particular performs the controlschemes described further below. Control system 500 can be embodied as asuitably-programmed general purpose computer comprising a centralprocessing unit, volatile and non-volatile storage devices, one or moreinput and output devices such as a keyboard and screen, one or morenetwork connections and one or more interfaces to the various parts ofthe lithographic apparatus. It will be appreciated that a one-to-onerelationship between controlling computer and lithographic apparatus isnot necessary. In an embodiment of the invention one computer cancontrol multiple lithographic apparatuses. In an embodiment of theinvention, multiple networked computers can be used to control onelithographic apparatus. The control system 500 may also be configured tocontrol one or more associated process devices and substrate handlingdevices in a lithocell or cluster of which the lithographic apparatusforms a part. The control system 500 can also be configured to besubordinate to a supervisory control system of a lithocell or clusterand/or an overall control system of a fab.

FIG. 3 shows a side view of a patterning device support according to anembodiment of the invention. The patterning device support generallydenoted by reference numeral 1 includes a long stroke part 2. The longstroke part 2 supports a short stroke part 3, and the short stroke part3 supports a patterning device holding structure or patterning deviceholder 4. The patterning device holding structure or patterning deviceholder 4 (e.g. the mask table) supports an exchangeable object. e.g.patterning device 5.

The long stroke part 2 is movably mounted with respect to a referenceobject 6, for instance a frame (such as e.g. a metrology frame). A longstroke actuator 7 is provided to move the long stroke part 2 withrespect to the reference object 6. The long stroke actuator 7 does notexert reaction forces on the reference object 6. A short stroke actuator8 is provided to move the short stroke part 3 with respect to the longstroke part 2. The short stroke actuator 8 has a relative high accuracyin positioning of the short stroke part 3 with respect to the longstroke part 2, but has a limited working range. The long stroke actuator7 has a large working range, typically the whole working space of thepatterning device support 1 and a relative low accuracy. The main taskof the long stroke actuator 8 is to bring the desired position of thepatterning device support 1 within the range of the short strokeactuator 8 so that the short stroke actuator 8 may position thepatterning device 5 with high accuracy.

A position measurement system 11 has been provided to measure theposition of the short stroke part 3 e.g. relative to the referenceobject 6. In an embodiment, the reference object 6 is the projectionlens PS or the metrology frame, MF. The position measurement system 11may be any system which is capable of measuring the position of theshort stroke part 3 with high accuracy, such as an interferometer systemor an encoder measurement system.

In order to isolate the short stroke part 3 from vibrations of the longstroke part 2, the short stroke actuator 8 may be of a type having a lowstiffness. Such actuator is for instance a Lorentz motor. The input ofthis type of actuator is an electrical current, proportional to thedesired force. The position response to an input force is somewhatdelayed because of calculation delay and delay in electronic components.This effect, together with higher-order dynamics, limits the bandwidthof the short-stroke control loop, which in turn limits the achievablestage positioning accuracy. In an alternative embodiment the shortstroke actuator 8 may be a reluctance actuator that is provided withflux feedback (as disclosed in US2012/0019794 herein incorporated in itsentirety by reference).

It is further remarked that the force-type short stroke actuator 8 alsolimits the achievable feed-forward effect from substrate table WT to thepatterning device support 1. In this feed-forward, the position error ofone stage is differentiated twice to create a feed-forward force, whichcosts one sample delay. This leads to a delayed response of the otherstage, limiting positioning accuracy of the stages relative to eachother.

Furthermore, due to the low stiffness of the short stroke actuator 8,during acceleration of the stage the full force desired for accelerationof the short stroke part 3 and patterning device holder 4 has to beexerted by the short stroke actuator 8. At the same time the shortstroke actuator 8 has to be capable of exerting small forces with highaccuracy to make precise positioning of the short stroke part 3. Thismakes the demand on the short stroke actuator 8, and the drivingelectronics like the amplifier, even higher.

With increasing demands on imaging accuracy and throughput, it isdesirable further to increase the accuracy and decrease the settlingtime in the positioning of exchangeable objects such as substrates orpatterning devices.

According to an embodiment of the present invention, an ultra shortstroke actuator 9 has been provided to cause movements between the shortstroke part 3 and the patterning device holding structure or patterningdevice holder 4. Between the short stroke part 3 and the patterningdevice holding structure or patterning device holder 4 one or more ultrashort stroke actuators 9 are arranged. These ultra short strokeactuators 9 have a relative high stiffness and are for instancepiezo-elements which create a movement between the short stroke part 3and the patterning device holding structure or patterning device holder4. This movement is typically smaller than about ±100 nm.

The ultra short stroke actuator 9 may have a relatively high stiffnessas the isolation of long-stroke vibrations is already performed by theshort stroke actuator 8 and possibly the long stroke actuator 7.Preferably, the ultra short stroke actuator 9 is a position typeactuator, i.e. it directly responds in terms of position. An example ofsuch position type actuator is a piezo-element which gives a deformationas a direct result of an electric voltage or charge.

A similar patterning device support is described in US 2009/0201477herein incorporated in its entirety by reference. The present inventionis directed to different control systems described with reference toFIGS. 5 and 6, a different physical implementation described withreference to FIGS. 3, 8 and 9 and to a calibrator described withreference to FIG. 7.

In an embodiment, the patterning device holder 4 is a table which issupported by an ultra short stroke actuator 9 on the short stroke part3. In an embodiment the ultra short stroke actuator 9 is adhered on oneside to the short stroke part 3 and on the other side to the patterningdevice holder 4. The ultra short stroke actuator 9 is desirably apiezoelectric stack, desirably a shear piezoelectric stack. In thisembodiment it is possible for the ultra short stroke actuator 9 tosupport the weight of the patterning device holder 4 and patterningdevice 5. The piezoelectric stack may be a shear piezoelectric stackallowing x y motion (motion in a plane perpendicular to the optical axisO of the apparatus). Each piezoelectric stack shears in both the x and ydirections. In an embodiment separate piezoelectric stacks may beprovided for movement only in the x direction and for movement only inthe y direction.

FIG. 4 illustrates a typical piezoelectric stack 91 of the ultra shortstroke actuator 9 in cross-section. The piezoelectric stack 91 comprisesinsulating material, electrodes and at least one layer of shearpiezoelectric material for shear movement. A typical thickness is about1 mm. In the embodiment of FIG. 4 outer layers 22 are inactive material(e.g. electrically insulating) with a thickness of typically 0.1 mm.Three electrode layers 24, 25, 26 are provided. The top two electrodes24, 25 are used to apply a potential difference across piezoelectriclayer 32 which may be for movement in the x direction and is between thetop two electrodes 24, 25. The bottom two electrodes 25, 26 are providedfor applying a potential difference across the second piezoelectriclayer 34 arranged for shear movement in the y direction and is betweenthe bottom two electrodes 25, 26. The electrode layers 24, 25, 26typically have a thickness of 0.1 mm and each piezoelectric shear layertypically has a thickness of 0.25 mm.

The benefit of positioning the ultra short stroke actuator 9 between thepatterning device holder 4 and short stroke actuator 8 is that thekinematic positioning by z supports (not illustrated) of the patterningdevice support 1 can be implemented as usual and the high x y stiffnessremains unaltered.

FIG. 5 shows a control scheme for the patterning device support 1. Thecontrol scheme is implemented under control of a single or multiplecontrollers each of which may or may not be part of the control system500.

In the embodiment of FIG. 5 an ultra short stroke actuator controller100 is present as well as a short stroke actuator controller 200. As aninput signal a set point SP_(rs) for the desired position of the shortstroke part 3 is provided. The desired position SP_(rs) of the shortstroke part 3 can be determined by the control system 500, for example.A simple control loop using the position measurement system 11 todetermine the actual position of the short stroke part 3 is used. Thesignal from the position measurement system 11 is subtracted from thedesired position SP_(rs) at comparator 255 of the short stroke actuatorcontroller 200. The output of comparator 255 is therefore an errorsignal e_(rs) relating to the positional error of the short stroke part3 which is a difference between a desired position of the short strokepart 3 relative to the reference object 6 and the actual position of theshort stroke part relative to the reference object 6. This signal isdenoted e_(rs) and is provided to a short stroke controller 250. On thebasis of this signal the short stroke controller 250 provides a controlsignal to the short stroke actuator 8 to move the short stroke part 3closer the desired position.

The error in position of the substrate stage can be determined bysubtracting the actual position of the substrate stage (for example, asmeasured by the position sensor IF described above with reference toFIG. 1) and a set point for the substrate stage (set, for example, bythe control system 500). The error in position of the substrate is asubstrate positional error e_(ws) which is a difference between adesired position of the substrate/substrate stage relative to areference object and an actual position of the substrate/substrate stagerelative to a reference object. Because the position of the substrate onthe substrate table is known, the positional error of the substratetable e_(ws) can be assumed to be the positional error of the substrateW. In an embodiment the error signal e_(ws) in FIG. 5 may be instead apositional error of the substrate itself rather than of the substratestage, although the two signals are actually indicative of the sameerror.

In the embodiment of FIG. 5 the ultra short stroke actuator controller100 is comprised of two control parts. This includes an open loopcontrol part 110 and a closed loop control part 150. The open and closedloop control parts 110, 150 and the short stroke controller 250 may eachbe part of the control system 500 or may be separate control parts whichtogether form a controller. The closed loop control part 150incorporates a comparator 155 and requires positional measurement of thepatterning device 5 or patterning device holder 4 using positionalmeasurement device 160. In an embodiment only the open loop control 110is used. In an embodiment only the closed loop controller 150 andassociated comparator and positional measurement device 160 are used.The positional measurement device 160 measures the position of thepatterning device 5 or patterning device holder 4 relative to the shortstroke part 3. Thus, the positional measurement device 160 measures theeffect of movement of the actuator 9. Alternatively, the positionmeasurement system 160 measures the position of the patterning device 5or patterning device holder 4 with respect to an object 6 (e.g. the samereference as measurement system 11), and the relative position of thepatterning device 5 or patterning device holder 4 with respect to theshort stroke part 3 is deducted from both position measurements 11 and160.

The open loop controller 110 works on the basis of a knowledge of theamount of deflection of the ultra short stroke actuator 9 for any givenapplied voltage, charge or current. A knowledge of the relationshipbetween applied voltage, charge or current and displacement can beobtained using a calibration technique as described below with referenceto FIG. 7 or this information can be provided, for example by themanufacturer of the ultra short stroke actuator 9. The knowledge orinformation may be stored on a memory of the open loop controller 110.In some instances the relationship between applied voltage, charge orcurrent and displacement may not be well known. In that case the openloop controller 110 may comprise a multiplier 111. The multiplier 111can set a multiplication factor of the position error signal e_(ws). Amultiplication factor of 1 is used, for example, where the relationshipbetween applied voltage or current and displacement is very well known.A lower multiplication factor might be applied in an embodiment wherethe relationship between applied voltage and/or current and displacementis less well known. Typically the multiplier 111 sets a multiplicationfactor of the positional error signal e_(ws) to be between 1 and 0.2.

The closed loop controller 150 works on the basis of feedback. Thecontroller 150 applies a control signal to the ultra short strokeactuator 9. The positional measurement device 160 records the change inposition of the patterning device 5 and/or patterning device holder 4relative to the short stroke part 3. The positional measurement device160 provides the signal to comparator 155. The comparator 155 subtractsthe signal from the positional measurement device 160 from thepositional error signal e_(ws). In this way the closed loop controller150 adjusts the position of the patterning device holder 4 based on afeedback loop.

In the embodiment of FIG. 5 where both the closed loop controller 150and open loop controller 110 are implemented, the signals from the twocontrollers are added by adder 170 and provided to the ultra shortstroke actuator 9.

In the embodiment of FIG. 5 the ultra short stroke actuator controller100 therefore controls the ultra short stroke actuator 9 exclusively onthe basis of the substrate positional error e_(ws) and optionally on themeasured position of the patterning device holder relative to themoveable structure.

If only the open loop controller 110 is used, the ultra short strokeactuator 9 is controlled only on the basis of the substrate positionalerror e_(ws). In the situation that no closed loop controller 150 isused, no active damping of the resonance due to the patterning device 5on the stiffness of the patterning device holder 4 occurs. In such asituation, it may be beneficially to damp the resonance by additionaldamping means. In a first embodiment, this is realized by creating anelectrical resonance at the same frequency of the mechanical resonanceand consequently to dissipate electrical energy into a resistance. In apreferred embodiment, a passive RL damping network is combined with thecharge amplifier that is used to drive the piezo actuator. In a secondembodiment, internal force feedback in the ultra short stroke actuator 9may be used. This requires an additional piezoelectric stack 91 actingas a sensor and providing position feedback to the actuating piezo. Sucha piezoelectric stack may be realized by combining two of thepiezoelectric stacks 91 as explained with reference to FIG. 4. Thecombination of an actuator piezo and a sensor piezo placed between thepatterning device holder 4 and the patterning device 5 forms together alocal closed-loop control system providing active damping. Suchadditional damping embodiments are beneficial as the required space nearthe patterning device 4/patterning device holder 5 may be limited inpractical situations. In a third embodiment the piezoelectric stack 91is simultaneously used as piezo actuator and as piezo sensor. This canbe realized by superposing a high frequent detection voltage on top ofthe applied (driving) voltage, wherein the frequency of the detectionvoltage exceeds the so-called Nyquist frequency. Based on the detectionvoltage a capacity change can be measured (e.g. by using a LCR-bridge)and consequently the position (elongation or compression) of thepiezoelectric stack can be derived. If alternatively or additionally theclosed loop controller 150 is used, the ultra short stroke actuator 9 ismoved only on the basis of the substrate positional error e_(ws) and themeasured position of the patterning device 5 and/or patterning deviceholder 4 relative to the short stroke part 3. The latter signal is usedin a feedback manner.

In an embodiment the ultra short stroke actuator controller 100 uses oneor both of the open loop controller 110 and closed loop controller 150and moves the ultra short stroke actuator 9 on the basis of a positionalerror other than the positional error of the substrate stage. Thepositional error might be an error in position of the short stroke part3, for example. In the embodiment of FIG. 6 the ultra short strokeactuator controller 100 has as its input both the error e_(ws) of thesubstrate stage and the error e_(rs) of the short stroke part.

The embodiment of FIG. 6 is the same as that of FIG. 5 except asdescribed below. In the embodiment of FIG. 6 both the short strokeactuator controller 200 and ultra short stroke actuator 100 drive theirrespective actuators at least partly on both the substrate positionalerror e_(ws) and the short stroke part error e_(rs). The substrate stageerror e_(ws) and short stroke part error e_(rs) are calculated in thesame way as described with reference to FIG. 5. The two signals areadded together by adders 120, 257 and are provided to correspondingcontrollers 100, 250. The ultra short stroke actuator controller 100 maythen operate in accordance with the embodiment described with referenceto FIG. 5 with one or both of the open loop controller 110 and closedloop controller 150 and positional measurement signal from positionalmeasurement device 160.

The dynamic response of the ultra short stroke actuator 9 is better thanthat of the short stroke actuator 8. However, a disadvantage of theultra short stroke actuator 9 is that for a large working range (forexample +/−200 nm) hysteresis, non-linearity and drift can be adifficulty. Piezo non-linearity is a non linear relationship betweenapplied voltage, charge or current and displacement and as a resultnon-linearity can result in extra difficulty in control of a piezoactuator. The embodiment of FIG. 6 addresses these issues by correctingfor the substrate stage positional error e_(ws) using both the ultrashort stroke actuator 9 and the short stroke actuator 8. This has thebenefit of reducing the required working range of the ultra short strokeactuator 9 to about +/−50 nm which reduces piezo non-linearity,hysteresis and drift.

In an embodiment a high band pass filter 130 and low band pass filter140 are provided. These are arranged such that substrate positionalerror e_(ws) (and/or short stroke part 3 errors e_(rs)) are filtered sothat error components with a high frequency (e.g. above a predeterminedmagnitude) are dealt with by the ultra short stroke actuator 9 whereaserror components with a low frequency (e.g. below the predeterminedmagnitude) are dealt with by the short stroke actuator 8. This isbeneficial as it takes advantage of strengths of each type of actuator.

The below table shows modeling results for the embodiment of FIG. 6illustrating in three columns the position error of the substrate WS-x,the results using only the short stroke actuator 8 to control forsubstrate stage positional errors WR, original and in the right handmost column the results for the FIG. 6 embodiment WR, piezo addition.The model assumes that there is no error in the position of the shortstroke part 3 (i.e. e_(rs) equals zero). The first row indicates themaximum moving average error in the image position, the second row themaximum moving standard deviation of the image position error and thenext two rows give the three sigma values of those two errors. As can beseen, a significant improvement is obtained using the ultra short strokeactuator 9 in addition to the short stroke actuator 8 to correct forerrors in substrate stage position.

[nm] WS-x WR, original WR, Piezo addition MA max 3.73 0.95 0.05 MSD max5.75 4.55 3.01 MA m + 3 s 2.25 0.58 0.03 MSD m + 3 s 4.33 4.49 3.27

Both the closed loop controller 150 and open loop controller 110 requiresome information regarding the relationship between displacement andapplied voltage or current for the ultra short stroke actuator 9. In anembodiment the controller 100 applies a known voltage, charge and/orcurrent to the actuator 9. A signal from the positional measurementdevice 160 is monitored to sense the amount of movement of thepatterning device 5 and/or patterning device holder 4. This informationcan be stored in a memory 180 of the controller 100 and be used by theopen loop controller 110 and/or closed loop controller 150.

FIG. 7 illustrates schematically a different way in which the ultrashort stroke actuator 100 can comprise a calibrator 170 which canestablish a relationship between applied voltage, charge and/or currentand displacement of the ultra short stroke actuator 9. In an embodimentthe controller 100 alternatively or additionally uses a signal from atransmission image sensor (TIS) 300 rather than from the positionalmeasurement device 160. The transmission image sensor 300 may beprovided on the substrate table WT, for example. The transmission imagesensor 300 can be used to determine the change in position of thepatterned beam of radiation down stream of the projection system (e.g.at the level of the substrate) following application or a change of anapplied voltage, charge and/or current to the ultra short strokeactuator 9. This information may be particularly useful in that itprovides a direct link between the voltage, charge or current applied tothe ultra short stroke actuator 9 by the controller 100 on the change inposition of the patterned image at the substrate level. Therefore, asignal relating the error in position of the substrate can be compareddirectly to the values obtained during calibration of the amount ofmovement of the patterned image and a corresponding voltage applied tothe ultra short stroke actuator 9 to correct for the error in position.

In US 2011/0222039, hereby incorporated in its entirety by reference,the idea of patterning device 5 bending is disclosed. In the embodimentof FIGS. 8 and 9 the ultra short stroke actuator 9 can be used in such asystem. In an embodiment the ultra short stroke actuator 9 is used toapply a force to the patterning device 5 in order to bend it. In anembodiment the ultra short stroke actuator 9 is used to reduce a forcebetween the patterning device holder 4 and the patterning device 5 aftera patterning device actuator 400 has been used to apply a torque or aforce to the patterning device 5 in order to bend it (as illustrated inFIG. 9 and described in US 2011/0222039).

As is illustrated in plan in FIG. 8, the ultra short stroke actuator 9may in fact be comprised of a plurality of piezoelectric stacks 91, 92.In an embodiment the individual piezoelectric stacks 91, 92 are providedaround a circumference of the object holder 4. For example, thepiezoelectric stacks 91, 92 may be provided equally spaced around thecircumference. Each of the piezoelectric stacks 91, 92 may beindividually controlled by the ultra short stroke actuator controller100. Therefore, in order to apply a force to the patterning device 5 orto reduce a force between the patterning device 5 and the patterningdevice holder 4 when a force is applied by a patterning device actuator400 to the patterning device 5, the ultra short stroke actuator stacks91, 92 may be used to impart a non constant force around thecircumference of the moveable member 4. In the example of FIG. 9, thepatterning device holder 4 is made to move radially inward by theplurality of piezoelectric stacks 91, 92 in the x-direction so as toreduce a force between the patterning device 5 and the patterning deviceholder 4. This reduces the likelihood of slippage between the patterningdevice holder 4 and patterning device 5; when the patterning device 5 isbent in the x-direction the distance in the x-direction between ends ofthe patterning device 5 becomes less. Without a corresponding reductionin the distance between parts of the patterning device holder 4 to whichthe patterning device 5 is attached, deleterious slippage between thepatterning device 5 and patterning device holder 4 may occur.

In an additional or alternative embodiment, heat loads applied to thepatterning device 5 which can result in thermal expansion/contraction ofthe patterning device and therefore the generation of forces between thepatterning device 5 and the patterning device holder 4 are compensated.These forces are reduced by the piezoelectric stacks 91, 92 as discussedabove. The control may require an estimate of the amount of thermalexpansion/contraction, for example based on a measured temperaturedistribution or measured stress/strain.

In an embodiment, the lithographic apparatus may comprise an encodersystem to measure the position, velocity, etc. of a component of theapparatus. In an embodiment, the component comprises a substrate table.In an embodiment, the component comprises a measurement and/or cleaningtable. The encoder system may be in addition to the interferometersystem described herein for the tables. The encoder system comprises asensor, transducer or read head associated, e.g., paired, with a scaleor grid. In an embodiment, the movable component (e.g., the substratetable and/or the measurement and/or cleaning table) has one or morescales or grids and a frame of the lithographic apparatus with respectto which the component moves has one or more of sensors, transducers orread heads. The one or more of sensors, transducers or read headscooperate with the scale(s) or grid(s) to determine the position,velocity, etc. of the component. In an embodiment, a frame of thelithographic apparatus with respect to which a component moves has oneor more scales or grids and the movable component (e.g., the substratetable and/or the measurement and/or cleaning table) has one or more ofsensors, transducers or read heads that cooperate with the scale(s) orgrid(s) to determine the position, velocity, etc. of the component.

As will be appreciated, any of the above described features can be usedwith any other feature and it is not only those combinations explicitlydescribed which are covered in this application.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications in manufacturing components with microscale, or evennanoscale features, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 365, 248, 193, 157 or 126 nm).

The term “lens”, where the context allows, may refer to any one orcombination of various types of optical components, including refractiveand reflective optical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the embodiments of the invention maytake the form of a computer program containing one or more sequences ofmachine-readable instructions describing a method as disclosed above, ora data storage medium (e.g. semiconductor memory, magnetic or opticaldisk) having such a computer program stored therein. Further, themachine readable instruction may be embodied in two or more computerprograms. The two or more computer programs may be stored on one or moredifferent memories and/or data storage media.

The controllers described above may have any suitable configuration forreceiving, processing, and sending signals. For example, each controllermay include one or more processors for executing the computer programsthat include machine-readable instructions for the methods describedabove. The controllers may also include data storage medium for storingsuch computer programs, and/or hardware to receive such medium.

One or more embodiments of the invention may be applied to any immersionlithographic apparatus, in particular, but not exclusively, those typesmentioned above, whether the immersion liquid is provided in the form ofa bath, only on a localized surface area of the substrate, or isunconfined on the substrate and/or substrate table. In an unconfinedarrangement, the immersion liquid may flow over the surface of thesubstrate and/or substrate table so that substantially the entireuncovered surface of the substrate table and/or substrate is wetted. Insuch an unconfined immersion system, the liquid supply system may notconfine the immersion liquid or it may provide a proportion of immersionliquid confinement, but not substantially complete confinement of theimmersion liquid.

A liquid supply system as contemplated herein should be broadlyconstrued. In certain embodiments, it may be a mechanism or combinationof structures that provides a liquid to a space between the projectionsystem and the substrate and/or substrate table. It may comprise acombination of one or more structures, one or more liquid inlets, one ormore gas inlets, one or more gas outlets, and/or one or more liquidoutlets that provide liquid to the space. In an embodiment, a surface ofthe space may be a portion of the substrate and/or substrate table, or asurface of the space may completely cover a surface of the substrateand/or substrate table, or the space may envelop the substrate and/orsubstrate table. The liquid supply system may optionally further includeone or more elements to control the position, quantity, quality, shape,flow rate or any other features of the liquid.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

1-20. (canceled)
 21. A lithographic apparatus comprising: a patterningdevice support constructed to support a patterning device, thepatterning device being capable of imparting a radiation beam with apattern in its cross-section to form a patterned radiation beam; asubstrate support constructed to hold a substrate; and a projectionsystem configured to project the patterned radiation beam onto a targetportion of the substrate, wherein the patterning device supportscomprises: a moveable structure movably arranged with respect to anobject, a patterning device holder movably arranged with respect to themovable structure and configured to hold the patterning device; anactuator configured to move the movable structure with respect to theobject; and an ultra short stroke actuator configured to move thepatterning device holder with respect to the movable structure andcomprising a plurality of actuators positioned around at least part of acircumference of the patterning device holder.
 22. The lithographicapparatus of claim 21, further comprising a controller configured tocontrol individual movement of each of the plurality of actuators of theultra short stroke actuator.
 23. The lithographic apparatus of claim 22,wherein the controller is configured to control movement of each of theplurality of actuators to compensate for patterning device deformationdue to uneven heat loads applied to the patterning device.
 24. Thelithographic apparatus of claim 22, further comprising an patterningdevice actuator configured to exert a torque or force on the patterningdevice and wherein the controller is configured to control movement ofeach of the plurality of actuators to reduce a force between thepatterning device and the patterning device holder resulting from thetorque or force exerted on the patterning device by the patterningdevice actuator. 25.-28. (canceled)
 29. The lithographic apparatus ofclaim 21, wherein the plurality of actuators are arranged along theentire circumference of the patterning device holder.
 30. Thelithographic apparatus of claim 21, wherein the plurality of actuatorscomprise a plurality of piezoelectric stacks.
 31. The lithographicapparatus of claim 30, wherein one or more of the plurality ofpiezoelectric stacks include an insulating material, electrodes and atleast one layer of shear piezoelectric material for shear movement. 32.The lithographic apparatus of claim 30, wherein at least one of theplurality of piezoelectric stacks is configured to provide a shearmovement in two perpendicular directions.
 33. The lithographic apparatusof claim 21, wherein the plurality of actuators are equally spacedaround the circumference.
 34. The lithographic apparatus of claim 21,wherein to apply a force to the patterning device or to reduce a forcebetween the patterning device and the patterning device holder when aforce is applied by a patterning device actuator to the patterningdevice, the plurality of actuators are configured to impart anon-constant force around the circumference of the patterning deviceholder.
 35. The lithographic apparatus of claim 21, wherein theplurality of actuators are configured to move the patterning deviceholder radially inward so as to reduce a force between the patterningdevice and the patterning device holder.
 36. The lithographic apparatusof claim 21, further comprising a liquid supply system configured tosupply liquid between a final element of the projection system and thesubstrate or the substrate support or both.
 37. A device manufacturingmethod comprising: patterning a radiation beam with a patterning deviceto form a patterned radiation beam, the patterning device being held bya patterning device holder that is movably arranged with respect to amovable structure; projecting, with a projection system, the patternedradiation beam onto a target portion of a substrate held on a substratetable, and moving the patterning device holder with respect to themovable structure using an ultra short stroke actuator, the ultra shortstroke actuator comprising a plurality of actuators positioned around atleast part of a circumference of the patterning device holder.
 38. Thedevice manufacturing method of claim 37, further comprising individuallycontrolling a movement of each of the plurality of actuators of theultra short stroke actuator.
 39. The device manufacturing method ofclaim 37, further comprising controlling a movement of each of theplurality of actuators to compensate for patterning device deformationdue to uneven heat loads applied to the patterning device.
 40. Thedevice manufacturing method of claim 37, further comprising exerting atorque or force on the patterning device and controlling a movement ofeach of the plurality of actuators to reduce a force between thepatterning device and the patterning device holder resulting from thetorque or force exerted on the patterning device.
 41. The devicemanufacturing method of claim 37, wherein the plurality of actuators arearranged along the entire circumference of the patterning device holder.42. The device manufacturing method of claim 37, wherein the pluralityof actuators comprise a plurality of piezoelectric stacks.
 43. Thedevice manufacturing method of claim 37, further comprising moving thepatterning device holder radially inward so as to reduce a force betweenthe patterning device and the patterning device holder.
 44. The devicemanufacturing method of claim 37, further supplying liquid between afinal element of the projection system and the substrate or thesubstrate table or both.